Mister Killkenny, I agree. Bipods and rests are better than slings when properly used by folks who know how to.
But niether's allowed in most rifle competitive disciplines with shoulder fired rifles. Nor are they typically carried by soldiers afield. A few hunters use bipods or will roll up a jacket to use as a rest.
That aside, there are folks who shoot match rifles slung up in prone that out perform most folks shooting the same rifle from a bench.
US Navy Distinguished Marksman Badge 153
Former US Navy & Palma Rifle Team Member
NRA High Power Master & Long Range High Master
NRA Smallbore Prone Master